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which_chick) wrote2020-05-04 09:55 pm
which_chick) wrote2020-05-04 09:55 pm
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A post of limited interest. Information wants to be free, though.
Okay, so in reviewing Tennessen on the Cordulegasters, he’s all “I believe that there are two subgroups of Cordulegaster, To Wit: Cordulegaster proper and Zoraena.” (Most odes people just lump these all in with Cordulegaster but Tennessen says LOL NOE, THEY ARE WAY DIFFERENT ON THE NYMPH SCALE and this difference is different enough to argue for Zoraena.)
For our purposes, as we have no axe to grind on the genus level, we can just treat this as an additional item in the key. Cordulegaster vs. Zoraena and then on from there. :) You will need a quite good hand lens and/or a decent light microscope because you are going to be counting hairs (okay, fine, setae) on ode larvae for this game.
Things that Tennessen calls Cordulegaster species:
diadema (elsewhere)
dorsalis (elsewhere)
erronea
maculata
obliqua
Things that Tennessen calls Zoraena:
bilineata
diastatops
sarracenia (elsewhere)
sayi (elsewhere)
talaria (elsewhere)
You’re in VA (says your post) so we’ll restrict the possibles to stuff that lives in VA, to wit:
erronea, maculata, obliqua (Tiger, twin-spotted, arrowhead – in order)
bilineata, diastatops (brown, delta-spotted, also in order)
First off, telling C’s from Z’s: You’re gonna look at several different features. All but one of them is on the face of your nymph.
1. Ventral view of prementum. Cordulegasters have a fairly V-shaped dish on the basal transverse suture. Z’s have a fairly straight-across basal transverse suture. (The prementum is basically what you’d think of as the big part of the “lower jaw” of these jobbies, and you’re looking at the underneath side of it.) I’ve included the diagram for this to show typical C vs. Z config.
(images are clickable if you need them bigger or whatever)
2. Dorsolateral rim of palpus (these are the little jaw things in front of the prementum, kind of… clasping jaw things with jaggedy teeth on the vertical front seam, dorsolateral rim is top-side of these. So… upper outside edge, oriented from the nymph’s point of view). You are looking at the setae, the not-hairs bristles or scales or whatever. Longest marginal setae 2.0 – 3.5 times the width of a primary setal base is C, Zs’ have setae 1-1.5x the width of a primary setal base. So, Cordulegasters have much longer marginal setae than Zoraena’s. Again, clearly ammie-level pic included.
3. Frontal ridge setae. The frontal ridge is on the face of your nymph, between the eyes and antennae. And we’re looking at the setae on it. For C’s there are at most 2-4 scattered piliform (piliform means hairlike) setae at most amongst a host of stouter setae. For Z’s there are a medial (in the middle) tuft of 8-12 piliform setae amongst the robuster ones. Lookit me all talking science and shit. Amazeballs.
4. Finally we’re looking at segment 8 of the body. If it has a posterolateral spine (a hook on the rear side of the segment) look at that spine. C’s have “curved upward slightly, directed toward S9 spine” whereas Z’s have “curved upward MARKEDLY, tip directed toward dorsad of S9 spine.)
Now, if you have a (Tennessen version) C you need to be able to tell them apart. Here’s what the book says. Our possibles are erronea, maculata, obliqua
We’re going to skip the first Key because it says longitude and we are east of 100 deg. West ( vertical line running a little to the west of the longest bottom point of Texas – VA is clearly not there and not even near there.)
Here we are looking at face structures again. There are diagrams, that I have included.
2. Palpal setae 4, marginal setae of frontal ridge rectangular to fan shaped. Short. Dorsum of body mostly beset with small, dark, flat setae and relatively few piliform setae. This is erronea.
2A: palpal setae 5-8, marginal setae of frontal ridge acuminate to blunt apically, elongate, dorsum of body mostly pale, piliform setae and or short, dark acuinate setae. Basically this is "Not 2". Go to 3.
3. Palpal setae usually 5 per side (94%) all marginal setae of frontal ridge pale, costal margin of wing sheaths with long pale setae only, prementum usually 5 or 6 primary setae on each side (90%) This is maculata.
3A. Palpal setae 6 per side, sometimes 7 or 8 one one side. Some marginal setae of frontal ridge dark. Costal margin of wing sheaths with both long and short dark setae. Prementum has 7 or 8 primary setae on each side, rarely 6. This is obliqua.
If you have a Tennessen Z, according to the first four points above, then you go to the Z section and start keying out those. We’re just going to do the ones that are possible for where you live. There’s no point doing ones that live in freaking Georgia or Florida or something. You’ve got bilineata or diastatops to work with here.
Diastatops: S3-S8 tergites (the upper side of larvae abdomen segments. “tergite” is … if the abdomen were covered in plate armor, which it is not, a tergite would be the “plate” for each piece. But you can probably see the lines and imagine what is meant, here.) with many short, fan-shaped setae interspersed with few slender setae, posterior margin of S8-S10 sternites beset mostly with flat, truncate setae. Palpal setae usually 5 per side (89%). (Tennessen says beset a lot. He likes it.)
Bilineata: S3-S7 tergites with nearly all setae piliform medially, very few if any blunt-tipped setae; antm 1 with blunt setae poststernum with 3 or 4 long stout setae medially and posterior margin of S1 sternum with few or no long piliform setae.
Again, there are pictures.
I hope that this has helped. I am not a bug science person but I have a bug science book. So there's that.
For our purposes, as we have no axe to grind on the genus level, we can just treat this as an additional item in the key. Cordulegaster vs. Zoraena and then on from there. :) You will need a quite good hand lens and/or a decent light microscope because you are going to be counting hairs (okay, fine, setae) on ode larvae for this game.
Things that Tennessen calls Cordulegaster species:
diadema (elsewhere)
dorsalis (elsewhere)
erronea
maculata
obliqua
Things that Tennessen calls Zoraena:
bilineata
diastatops
sarracenia (elsewhere)
sayi (elsewhere)
talaria (elsewhere)
You’re in VA (says your post) so we’ll restrict the possibles to stuff that lives in VA, to wit:
erronea, maculata, obliqua (Tiger, twin-spotted, arrowhead – in order)
bilineata, diastatops (brown, delta-spotted, also in order)
First off, telling C’s from Z’s: You’re gonna look at several different features. All but one of them is on the face of your nymph.
1. Ventral view of prementum. Cordulegasters have a fairly V-shaped dish on the basal transverse suture. Z’s have a fairly straight-across basal transverse suture. (The prementum is basically what you’d think of as the big part of the “lower jaw” of these jobbies, and you’re looking at the underneath side of it.) I’ve included the diagram for this to show typical C vs. Z config.
(images are clickable if you need them bigger or whatever)
2. Dorsolateral rim of palpus (these are the little jaw things in front of the prementum, kind of… clasping jaw things with jaggedy teeth on the vertical front seam, dorsolateral rim is top-side of these. So… upper outside edge, oriented from the nymph’s point of view). You are looking at the setae, the not-hairs bristles or scales or whatever. Longest marginal setae 2.0 – 3.5 times the width of a primary setal base is C, Zs’ have setae 1-1.5x the width of a primary setal base. So, Cordulegasters have much longer marginal setae than Zoraena’s. Again, clearly ammie-level pic included.
3. Frontal ridge setae. The frontal ridge is on the face of your nymph, between the eyes and antennae. And we’re looking at the setae on it. For C’s there are at most 2-4 scattered piliform (piliform means hairlike) setae at most amongst a host of stouter setae. For Z’s there are a medial (in the middle) tuft of 8-12 piliform setae amongst the robuster ones. Lookit me all talking science and shit. Amazeballs.
4. Finally we’re looking at segment 8 of the body. If it has a posterolateral spine (a hook on the rear side of the segment) look at that spine. C’s have “curved upward slightly, directed toward S9 spine” whereas Z’s have “curved upward MARKEDLY, tip directed toward dorsad of S9 spine.)
Now, if you have a (Tennessen version) C you need to be able to tell them apart. Here’s what the book says. Our possibles are erronea, maculata, obliqua
We’re going to skip the first Key because it says longitude and we are east of 100 deg. West ( vertical line running a little to the west of the longest bottom point of Texas – VA is clearly not there and not even near there.)
Here we are looking at face structures again. There are diagrams, that I have included.
2. Palpal setae 4, marginal setae of frontal ridge rectangular to fan shaped. Short. Dorsum of body mostly beset with small, dark, flat setae and relatively few piliform setae. This is erronea.
2A: palpal setae 5-8, marginal setae of frontal ridge acuminate to blunt apically, elongate, dorsum of body mostly pale, piliform setae and or short, dark acuinate setae. Basically this is "Not 2". Go to 3.
3. Palpal setae usually 5 per side (94%) all marginal setae of frontal ridge pale, costal margin of wing sheaths with long pale setae only, prementum usually 5 or 6 primary setae on each side (90%) This is maculata.
3A. Palpal setae 6 per side, sometimes 7 or 8 one one side. Some marginal setae of frontal ridge dark. Costal margin of wing sheaths with both long and short dark setae. Prementum has 7 or 8 primary setae on each side, rarely 6. This is obliqua.
If you have a Tennessen Z, according to the first four points above, then you go to the Z section and start keying out those. We’re just going to do the ones that are possible for where you live. There’s no point doing ones that live in freaking Georgia or Florida or something. You’ve got bilineata or diastatops to work with here.
Diastatops: S3-S8 tergites (the upper side of larvae abdomen segments. “tergite” is … if the abdomen were covered in plate armor, which it is not, a tergite would be the “plate” for each piece. But you can probably see the lines and imagine what is meant, here.) with many short, fan-shaped setae interspersed with few slender setae, posterior margin of S8-S10 sternites beset mostly with flat, truncate setae. Palpal setae usually 5 per side (89%). (Tennessen says beset a lot. He likes it.)
Bilineata: S3-S7 tergites with nearly all setae piliform medially, very few if any blunt-tipped setae; antm 1 with blunt setae poststernum with 3 or 4 long stout setae medially and posterior margin of S1 sternum with few or no long piliform setae.
Again, there are pictures.
I hope that this has helped. I am not a bug science person but I have a bug science book. So there's that.